// copy-relocs.cc -- handle COPY relocations for gold.
// Copyright (C) 2006-2018 Free Software Foundation, Inc.
// Written by Ian Lance Taylor <iant@google.com>.
// This file is part of gold.
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 3 of the License, or
// (at your option) any later version.
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
// MA 02110-1301, USA.
#include "gold.h"
#include "symtab.h"
#include "copy-relocs.h"
namespace gold
{
// Copy_relocs methods.
// Handle a relocation against a symbol which may force us to generate
// a COPY reloc.
template<int sh_type, int size, bool big_endian>
void
Copy_relocs<sh_type, size, big_endian>::copy_reloc(
Symbol_table* symtab,
Layout* layout,
Sized_symbol<size>* sym,
Sized_relobj_file<size, big_endian>* object,
unsigned int shndx,
Output_section* output_section,
unsigned int r_type,
typename elfcpp::Elf_types<size>::Elf_Addr r_offset,
typename elfcpp::Elf_types<size>::Elf_Swxword r_addend,
Output_data_reloc<sh_type, true, size, big_endian>* reloc_section)
{
if (this->need_copy_reloc(sym, object, shndx))
this->make_copy_reloc(symtab, layout, sym, object, reloc_section);
else
{
// We may not need a COPY relocation. Save this relocation to
// possibly be emitted later.
this->save(sym, object, shndx, output_section,
r_type, r_offset, r_addend);
}
}
// Return whether we need a COPY reloc for a relocation against SYM.
// The relocation is begin applied to section SHNDX in OBJECT.
template<int sh_type, int size, bool big_endian>
bool
Copy_relocs<sh_type, size, big_endian>::need_copy_reloc(
Sized_symbol<size>* sym,
Sized_relobj_file<size, big_endian>* object,
unsigned int shndx) const
{
if (!parameters->options().copyreloc())
return false;
if (sym->symsize() == 0)
return false;
// If this is a readonly section, then we need a COPY reloc.
// Otherwise we can use a dynamic reloc. Note that calling
// section_flags here can be slow, as the information is not cached;
// fortunately we shouldn't see too many potential COPY relocs.
if ((object->section_flags(shndx) & elfcpp::SHF_WRITE) == 0)
return true;
return false;
}
// Emit a COPY relocation for SYM.
template<int sh_type, int size, bool big_endian>
void
Copy_relocs<sh_type, size, big_endian>::emit_copy_reloc(
Symbol_table* symtab,
Sized_symbol<size>* sym,
Output_data* posd,
off_t offset,
Output_data_reloc<sh_type, true, size, big_endian>* reloc_section)
{
// Define the symbol as being copied.
symtab->define_with_copy_reloc(sym, posd, offset);
// Add the COPY relocation to the dynamic reloc section.
reloc_section->add_global_generic(sym, this->copy_reloc_type_, posd,
offset, 0);
}
// Make a COPY relocation for SYM and emit it.
template<int sh_type, int size, bool big_endian>
void
Copy_relocs<sh_type, size, big_endian>::make_copy_reloc(
Symbol_table* symtab,
Layout* layout,
Sized_symbol<size>* sym,
Sized_relobj_file<size, big_endian>* object,
Output_data_reloc<sh_type, true, size, big_endian>* reloc_section)
{
// We should not be here if -z nocopyreloc is given.
gold_assert(parameters->options().copyreloc());
gold_assert(sym->is_from_dynobj());
// The symbol must not have protected visibility.
if (sym->is_protected())
{
gold_error(_("%s: cannot make copy relocation for "
"protected symbol '%s', defined in %s"),
object->name().c_str(),
sym->name(),
sym->object()->name().c_str());
}
typename elfcpp::Elf_types<size>::Elf_WXword symsize = sym->symsize();
// There is no defined way to determine the required alignment of
// the symbol. We know that the symbol is defined in a dynamic
// object. We start with the alignment of the section in which it
// is defined; presumably we do not require an alignment larger than
// that. Then we reduce that alignment if the symbol is not aligned
// within the section.
bool is_ordinary;
unsigned int shndx = sym->shndx(&is_ordinary);
gold_assert(is_ordinary);
typename elfcpp::Elf_types<size>::Elf_WXword addralign;
bool is_readonly = false;
{
// Lock the object so we can read from it. This is only called
// single-threaded from scan_relocs, so it is OK to lock.
// Unfortunately we have no way to pass in a Task token.
const Task* dummy_task = reinterpret_cast<const Task*>(-1);
Object* obj = sym->object();
Task_lock_obj<Object> tl(dummy_task, obj);
addralign = obj->section_addralign(shndx);
if (parameters->options().relro())
{
if ((obj->section_flags(shndx) & elfcpp::SHF_WRITE) == 0)
is_readonly = true;
else
{
// Symbols in .data.rel.ro should also be treated as read-only.
if (obj->section_name(shndx) == ".data.rel.ro")
is_readonly = true;
}
}
}
typename Sized_symbol<size>::Value_type value = sym->value();
while ((value & (addralign - 1)) != 0)
addralign >>= 1;
// Mark the dynamic object as needed for the --as-needed option.
sym->object()->set_is_needed();
Output_data_space* dynbss;
if (is_readonly)
{
if (this->dynrelro_ == NULL)
{
this->dynrelro_ = new Output_data_space(addralign, "** dynrelro");
layout->add_output_section_data(".data.rel.ro",
elfcpp::SHT_PROGBITS,
elfcpp::SHF_ALLOC | elfcpp::SHF_WRITE,
this->dynrelro_, ORDER_RELRO, false);
}
dynbss = this->dynrelro_;
}
else
{
if (this->dynbss_ == NULL)
{
this->dynbss_ = new Output_data_space(addralign, "** dynbss");
layout->add_output_section_data(".bss",
elfcpp::SHT_NOBITS,
elfcpp::SHF_ALLOC | elfcpp::SHF_WRITE,
this->dynbss_, ORDER_BSS, false);
}
dynbss = this->dynbss_;
}
if (addralign > dynbss->addralign())
dynbss->set_space_alignment(addralign);
section_size_type dynbss_size =
convert_to_section_size_type(dynbss->current_data_size());
dynbss_size = align_address(dynbss_size, addralign);
section_size_type offset = dynbss_size;
dynbss->set_current_data_size(dynbss_size + symsize);
this->emit_copy_reloc(symtab, sym, dynbss, offset, reloc_section);
}
// Save a relocation to possibly be emitted later.
template<int sh_type, int size, bool big_endian>
void
Copy_relocs<sh_type, size, big_endian>::save(
Symbol* sym,
Sized_relobj_file<size, big_endian>* object,
unsigned int shndx,
Output_section* output_section,
unsigned int r_type,
typename elfcpp::Elf_types<size>::Elf_Addr r_offset,
typename elfcpp::Elf_types<size>::Elf_Swxword r_addend)
{
this->entries_.push_back(Copy_reloc_entry(sym, r_type, object, shndx,
output_section, r_offset,
r_addend));
}
// Emit any saved relocs.
template<int sh_type, int size, bool big_endian>
void
Copy_relocs<sh_type, size, big_endian>::emit(
Output_data_reloc<sh_type, true, size, big_endian>* reloc_section)
{
for (typename Copy_reloc_entries::iterator p = this->entries_.begin();
p != this->entries_.end();
++p)
{
Copy_reloc_entry& entry = *p;
// If the symbol is no longer defined in a dynamic object, then we
// emitted a COPY relocation, and we do not want to emit this
// dynamic relocation.
if (entry.sym_->is_from_dynobj())
reloc_section->add_global_generic(entry.sym_, entry.reloc_type_,
entry.output_section_, entry.relobj_,
entry.shndx_, entry.address_,
entry.addend_);
}
// We no longer need the saved information.
this->entries_.clear();
}
// Instantiate the templates we need.
#ifdef HAVE_TARGET_32_LITTLE
template
class Copy_relocs<elfcpp::SHT_REL, 32, false>;
template
class Copy_relocs<elfcpp::SHT_RELA, 32, false>;
#endif
#ifdef HAVE_TARGET_32_BIG
template
class Copy_relocs<elfcpp::SHT_REL, 32, true>;
template
class Copy_relocs<elfcpp::SHT_RELA, 32, true>;
#endif
#ifdef HAVE_TARGET_64_LITTLE
template
class Copy_relocs<elfcpp::SHT_REL, 64, false>;
template
class Copy_relocs<elfcpp::SHT_RELA, 64, false>;
#endif
#ifdef HAVE_TARGET_64_BIG
template
class Copy_relocs<elfcpp::SHT_REL, 64, true>;
template
class Copy_relocs<elfcpp::SHT_RELA, 64, true>;
#endif
} // End namespace gold.